Folded lens system with four refractive lenses

ABSTRACT

Compact folded lens systems are described that may be used in small form factor cameras. Lens systems are described that may include four lens elements with refractive power, with a light folding element such as a prism, located between a first lens element on the object side of the lens system and a second lens element, that redirects the light refracted from the first lens element from a first axis onto a second axis on which the other lens elements and a photosensor are arranged. The lens systems may include an aperture stop located behind the front vertex of the lens system, for example at the first lens element, and an optional infrared filter, for example located between the last lens element and a photosensor.

PRIORITY INFORMATION

This application claims benefit of priority of U.S. ProvisionalApplication Ser. No. 62/314,350 entitled “FOLDED TELEPHOTO LENS SYSTEMS”filed Mar. 28, 2016, the content of which is incorporated by referenceherein in its entirety, and also claims benefit of priority of U.S.Provisional Application Ser. No. 62/334,398 entitled “FOLDED LENS SYSTEMWITH FOUR REFRACTIVE LENSES” filed May 10, 2016, the content of which isincorporated by reference herein in its entirety.

BACKGROUND Technical Field

This disclosure relates generally to camera systems, and morespecifically to compact lens systems for high-resolution, small formfactor camera systems.

Description of the Related Art

The advent of small, mobile multipurpose devices such as smartphones andtablet or pad devices has resulted in a need for high-resolution, smallform factor cameras for integration in the devices. However, due tolimitations of conventional camera technology, conventional smallcameras used in such devices tend to capture images at lower resolutionsand/or with lower image quality than can be achieved with larger, higherquality cameras. Achieving higher resolution with small package sizecameras generally requires use of a photosensor (also referred to as animage sensor) with small pixel size and a good, compact imaging lenssystem. Advances in technology have achieved reduction of the pixel sizein photosensors. However, as photosensors become more compact andpowerful, demand for compact imaging lens system with improved imagingquality performance has increased.

SUMMARY OF EMBODIMENTS

Compact folded lens systems are described that may be used in small formfactor cameras. Lens systems are described that may include four lenselements with refractive power, with a light folding element such as aprism located between a first lens element on the object side of thelens system and a second lens element that redirects the light refractedfrom the first lens element from a first axis onto a second axis onwhich the other lens elements and a photosensor are arranged. The lenssystems may include an aperture stop located behind the front vertex ofthe lens system, for example at the first lens element, and an optionalinfrared filter, for example located between the last lens element and aphotosensor of the camera.

Embodiments of the compact folded lens system may include four lenselements with refractive power and a light folding element such as aprism to fold the optical axis. The compact folded lens system may beconfigured to operate with a relatively narrow field of view and a 35 mmequivalent focal length (f_(35 mm)) in the telephoto range. For example,some embodiments of the compact folded lens system may provide a 35 mmequivalent focal length in the range of 55-140 mm, with less than 6.5 mmof Z-height to fit in a wide variety of portable electronics devices.

Through proper arrangement in materials, power and radius of curvatureof the four lens elements with power, embodiments of the compact foldedlens are capable of capturing high resolution, high quality images atgood brightness level. In some embodiments, a first lens element fromthe object side of the lens system has a convex object-side surface inthe paraxial region, and a third lens element has a concave image-sidesurface in the paraxial region. In some embodiments, a first lenselement from the object side of the lens system has a convex object-sidesurface in the paraxial region, and a third lens element has a concaveimage-side surface in the paraxial region. In some embodiments, thefirst lens elements is formed of optical materials with Abbe numberVd>40, and the second lens element is formed of an optical material withAbbe number Vd<30. In some embodiments, the first and fourth lenselements are formed of optical materials with Abbe number Vd>40, and thesecond lens element is formed of an optical material with Abbe numberVd<30.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional illustration of a compact camera includingan example embodiment of a compact folded lens system with four lenselements and a light folding element.

FIGS. 2A and 2B show a camera that includes an example embodiment of acompact folded lens system that operates at F/2.4, with 31° full fieldof view (FOV).

FIG. 3 shows a camera that includes an example embodiment of a compactfolded lens system that operates at F/2.4, with 28.1° full FOV.

FIG. 4 shows a camera that includes an example embodiment of a compactfolded lens system that operates at F/2.2, with 42.2° full FOV.

FIG. 5 shows a camera that includes an example embodiment of a compactfolded lens system that operates at F/2.6, with 23.7° full FOV.

FIG. 6 shows a camera that includes an example embodiment of a compactfolded lens system that operates at F/2.4, with 31.2° full FOV.

FIG. 7 shows a camera that includes an example embodiment of a compactfolded lens system that operates at F/3, with 20.4° full FOV.

FIG. 8 illustrates numbering of the surfaces in the example lens systemsas used in the Tables.

FIG. 9 is a flowchart of a method for capturing images using cameraswith lens systems as illustrated FIGS. 1 through 7, according to someembodiments.

FIG. 10 illustrates an example computer system that may be used inembodiments.

This specification includes references to “one embodiment” or “anembodiment.” The appearances of the phrases “in one embodiment” or “inan embodiment” do not necessarily refer to the same embodiment.Particular features, structures, or characteristics may be combined inany suitable manner consistent with this disclosure.

“Comprising.” This term is open-ended. As used in the appended claims,this term does not foreclose additional structure or steps. Consider aclaim that recites: “An apparatus comprising one or more processor units. . . ”. Such a claim does not foreclose the apparatus from includingadditional components (e.g., a network interface unit, graphicscircuitry, etc.).

“Configured To.” Various units, circuits, or other components may bedescribed or claimed as “configured to” perform a task or tasks. In suchcontexts, “configured to” is used to connote structure by indicatingthat the units/circuits/components include structure (e.g., circuitry)that performs those task or tasks during operation. As such, theunit/circuit/component can be said to be configured to perform the taskeven when the specified unit/circuit/component is not currentlyoperational (e.g., is not on). The units/circuits/components used withthe “configured to” language include hardware—for example, circuits,memory storing program instructions executable to implement theoperation, etc. Reciting that a unit/circuit/component is “configuredto” perform one or more tasks is expressly intended not to invoke 35U.S.C. §112, sixth paragraph, for that unit/circuit/component.Additionally, “configured to” can include generic structure (e.g.,generic circuitry) that is manipulated by software and/or firmware(e.g., an FPGA or a general-purpose processor executing software) tooperate in manner that is capable of performing the task(s) at issue.“Configure to” may also include adapting a manufacturing process (e.g.,a semiconductor fabrication facility) to fabricate devices (e.g.,integrated circuits) that are adapted to implement or perform one ormore tasks.

“First,” “Second,” etc. As used herein, these terms are used as labelsfor nouns that they precede, and do not imply any type of ordering(e.g., spatial, temporal, logical, etc.). For example, a buffer circuitmay be described herein as performing write operations for “first” and“second” values. The terms “first” and “second” do not necessarily implythat the first value must be written before the second value.

“Based On.” As used herein, this term is used to describe one or morefactors that affect a determination. This term does not forecloseadditional factors that may affect a determination. That is, adetermination may be solely based on those factors or based, at least inpart, on those factors. Consider the phrase “determine A based on B.”While in this case, B is a factor that affects the determination of A,such a phrase does not foreclose the determination of A from also beingbased on C. In other instances, A may be determined based solely on B.

DETAILED DESCRIPTION

Embodiments of a compact folded lens system including four lens elementswith refractive power, with a light folding element such as a prismlocated between a first lens element on the object side of the lenssystem and a second lens element that redirects the light refracted fromthe first lens element from a first axis onto a second axis on which theother lens elements and a photosensor are arranged. The lens system mayinclude an aperture stop located behind the front vertex of the lenssystem, for example at the first lens element, and an optional infraredfilter, for example located between the last lens element and thephotosensor. The shapes, materials, and arrangements of the lenselements in the lens system may be selected to capture high resolution,high quality images.

Conventionally, compact imaging lenses can be designed with a non-foldedoptical axis that provide a 35 mm equivalent focal length (f_(35 mm)) of50mm-70 mm. However, the lens brightness (related to the focal ratio, orF/#, of the lens system) and image quality of these conventional compactlens designs are typically limited by the constraint in thickness (Zdimension) of portable electronics devices. It is difficult to furtherincrease the lens effective focal length of these conventional compactlens designs due to the scaling relationship with respect to the lensdimensions. To overcome this limitation, a folding-prism or mirror maybe used in embodiments to relieve the constraint in the Z dimension ofthe lens system.

Embodiments of the compact folded lens systems as described herein mayprovide high resolution, high quality imaging for small form factorcameras. Using an embodiment of the compact lens system, a camera may beimplemented in a small package size while still capturing sharp,high-resolution images, making embodiments of the camera suitable foruse in small and/or mobile multipurpose devices such as cell phones,smartphones, pad or tablet computing devices, laptop, netbook, notebook,subnotebook, and ultrabook computers, and so on. FIG. 10 illustrates anexample device that may include one or more small form factor camerasthat use embodiments of the compact folded lens systems as describedherein. However, note that aspects of the camera (e.g., the lens systemand photosensor) may be scaled up or down to provide cameras with largeror smaller package sizes. In addition, embodiments of the camera systemmay be implemented as stand-alone digital cameras. In addition to still(single frame capture) camera applications, embodiments of the camerasystem may be adapted for use in video camera applications.

Folded Lens Systems with Four Lens Elements

FIG. 1 is a cross-sectional illustration of a compact camera 100including an example embodiment of a compact folded lens system 110 withfour lens elements 101-104 and a light folding element 140 such as aprism that “folds” the optical axis of the lens system 110. The camera100 may also include an aperture stop 130, an optional IR filter 150,and a photosensor 120. A compact camera 100 including an embodiment ofthe compact folded lens system 110 as illustrated in FIG. 1 may, forexample, be implemented in portable electronic devices such as mobilephones and tablets. For embodiments of a lens system 110 as illustratedin FIG. 1, the 35 mm equivalent focal length (f_(35 mm)) of the lenssystem 110 is longer than 50 mm. A compact folded lens system 110 havinga long f_(35 mm) may, for example, be used stand-alone for telephotophotography, or can be paired with a wide-angle imaging lens in adual-prime configuration to enable effective optical zoom for portableelectronic devices.

Embodiments of a compact folded lens system 110 are described thatinclude four lens elements 101-104 with refractive power and a lightfolding element 140 such as a prism to fold the optical axis.Embodiments of the compact folded lens system 110 may provide a 35 mmequivalent focal length in the range of 75-120 mm and less than 6 mm ofZ-height to fit in a wide variety of portable electronics devices. Withproper arrangement of materials and lens powers, embodiments of thecompact folded lens system 110 are capable of capturing high brightnessphotos with high image quality.

As illustrated in the example camera 100 of FIG. 1, the compact foldedlens system 110 includes four elements with refractive power and a lightfolding element 140 (e.g., a prism), in order from the object side tothe image side of the lens system 100: a first lens element 101 withpositive refractive power; a folding element 140 such as a prism to foldthe optical axis from AX1 to AX2; a second lens element 102 withnegative refractive power; a third lens element 103 with refractivepower; and a fourth lens element 104 with refractive power. An aperturestop 130 may be located between the object side of the lens system 110and the folding element 140 for controlling the brightness of theoptical system.

In some embodiments, the camera 100 includes an IR filter 150 to reduceor eliminate interference of environmental noises on the photosensor120. In some embodiments, the photosensor 120 and/or lens system 110 maybe shifted along AX2 to allow refocusing of the lens system 110 inbetween Infinity conjugate and Macro conjugate. In various embodiments,lens element 102, lens element 103, and/or lens element 104 may beround/circular, rectangular, or some other shape.

In embodiments of lens system 110, one or more of the followingrequirements may be satisfied, for example to facilitate correction ofaberrations across the field of view (FOV) for the lens system 110:

-   -   Lens element 101 has a convex object-side surface in the        paraxial region.    -   Lens element 103 has a concave image-side surface in the        paraxial region.    -   In various embodiments, the other lens surfaces of lens elements        101 through 104 may be concave, convex, or flat/plano (e.g., the        lenses may be plano-concave or plano-convex lenses) in the        paraxial region.    -   In some embodiments, at least one of the eight lens surfaces may        be aspheric.    -   In some embodiments, at least one of the lens elements is made        of lightweight polymer or plastic material.    -   In some embodiments, lens element 101 and lens element 104 are        formed of optical materials with Abbe number Vd>40, and lens        element 102 is formed of an optical material with Abbe number        Vd<30. The material and power configurations of the lens        elements 101, 102, and 104 are selected for reduction of        chromatic aberrations.    -   In some embodiments, lens element 103 is formed of optical        material with no limit in Abbe number.

FIG. 1 shows an example camera 100 that includes an example embodimentsof a compact folded lens system 110 that operates at F/2.4, 31° fullfield of view. Camera 100 includes a 5.04 mm diagonal photosensor 120.The effective focal length (EFL) of the lens system 110 is 9 mm. Giventhe EFL and photosensor size, the 35 mm equivalent focal length of thecamera 100 is as large as 77 mm. In some embodiments, the camera100/lens system 110 has the capability of autofocusing from 400 mm toInfinity conjugates.

The modulation transfer functions (MTFs) for lens system 110 whenfocused at Infinity and Macro (400 mm) conjugates, at all fields andboth conjugates, are higher than 0.6 at 125 line pairs (lp)/mm spatialfrequency and higher than 0.3 at 150 lp/mm spatial frequency, providinggood contrast for high-resolution imaging. At both conjugates, theon-axis and off-axis aberrations for lens system 110 are well balancedacross the FOV. At both conjugates, optical distortion across the FOV iscontrolled within 1%, while field curvature and astigmatism are wellbalanced across the FOV.

In some embodiments, Z-height of the example lens system 110, as definedfrom the front vertex of lens element 101 to the rear vertex of thefolding element 140 may be 4.9 mm. The lens system 110 is thus able tofit into a wide variety of portable electronic devices including but notlimited to smart phones and tablets.

Folded Lens Systems with Four Lens Elements—Alternative embodiments

FIGS. 2A through 7 show several alternative embodiments of compactcameras with compact folded lens systems with four lens elements and alight folding element such as a prism that “folds” the optical axis ofthe lens system. A compact camera including an embodiment of the compactfolded lens systems as illustrated in FIGS. 2A through 7 may, forexample, be implemented in portable electronic devices such as mobilephones and tablets. The lens system and/or camera may also include anaperture stop, an optional infrared (IR) filter, and a photosensor. Thecompact folded lens systems as illustrated in FIGS. 2A through 7 may beconfigured to operate with a relatively narrow field of view and a 35 mmequivalent focal length (f_(35 mm)) in the telephoto range. Compactcameras including the compact folded lens systems as illustrated inFIGS. 2A through 7 may, for example, be used stand-alone for telephotophotography, or can be paired with a wide-angle imaging lens in adual-prime configuration to enable effective optical zoom for portableelectronic devices.

Embodiments of the compact folded lens system as illustrated in FIGS. 2Athrough 7 may include four lens elements with refractive power and alight folding element such as a prism to fold the optical axis.Embodiments of the compact folded lens system as illustrated in FIGS. 2Athrough 7 may provide a 35 mm equivalent focal length in the range of55-140 mm and less than 6.5 mm of Z-height to fit in a wide variety ofportable electronics devices. With proper arrangement in materials,power and radius of curvature of the three lens elements with power,embodiments of the compact folded lens system as illustrated in FIGS. 2Athrough 7 are capable of capturing high resolution, high quality imagesat good brightness level.

Embodiments of the compact folded lens system as illustrated in FIGS. 2Athrough 7 include four lens elements with refractive power and a foldingelement such as a prism, in order from the object side to the image sideof the lens system: a first lens element (lens 1) with positiverefractive power, a folding element such as a prism to fold the opticalaxis from AX1 to AX2, a second lens element (lens 2) with negativerefractive power, a third lens element (lens 3) with refractive power,and a fourth lens element (lens 4) with refractive power. An aperturestop may be located between the object side of the lens system and thefolding element for controlling the brightness of the optical system. Insome embodiments, the lens system or camera includes an IR filter toreduce or eliminate interference of environmental noises on the imagesensor (also referred to herein as a photosensor or sensor). In someembodiments, the photosensor may be shifted along AX2 to allowrefocusing of the lens system in between Infinity conjugate and Macroconjugate, for example for autofocus applications. Lenses 2, 3, and 4may be round/circular optical lenses, or may have a shape other thancircular (e.g., rectangular or square, hexagonal, etc.) to reduce thecamera module Z height.

In embodiments of the compact folded lens system as illustrated in FIGS.2A through 7, one or more of the following requirements may besatisfied, for example to facilitate correction of aberrations acrossthe field of view (FOV) for the lens system:

-   -   Lens 1 has a convex object-side surface in the paraxial region.    -   Lens 3 has a concave image side surface in the paraxial region.    -   In various embodiments, the other lens surfaces of lenses 1        through 4 may be concave, convex, or flat/plano (e.g., the        lenses may be plano-concave or plano-convex lenses) in the        paraxial region.    -   In some embodiments, at least one of the eight lens surfaces may        be aspheric.    -   In some embodiments, at least one of the lens elements is made        of a lightweight polymer or plastic.    -   In some embodiments, Lens 1 is formed of optical materials with        Abbe number Vd>40, and Lens 2 is formed of an optical material        with Abbe number Vd<30. The material and power configurations of        the lenses may, for example, be selected for reduction of        chromatic aberrations.    -   In some embodiments, one or more of the following relationships        may be met:

0.4<|f/f1|<1

0.8<|f/f2|<1.6

0.05<|R4f−R4r|/|R4f+R4r|<0.8

-   -   where f is effective focal length of the lens system, f1 is        focal length of lens 1, f2 is focal length of lens 2, R4 f is        radius of curvature of the object-side surface of lens 4, and R4        r is radius of curvature of the image side surface of lens 4.

As shown in the example embodiment in FIGS. 2A-2B, in some embodimentsof a camera including compact folded lens system as illustrated in FIGS.2A through 7, the photosensor may be moved on one or more axes relativeto the lens system to adjust focus of the camera. Alternatively, in someembodiments, the lens system may be moved relative to the photosensor toadjust focus. FIG. 2A corresponds to the camera focused at a firstposition (infinity conjugate), and FIG. 2B corresponds to the camerafocused at a second position (e.g., macro conjugate). While the focuspositions are shown as examples, note that the camera may be focused atother positions in some embodiments.

As shown in the example embodiments in FIGS. 2A-7, in some embodimentsof a compact folded lens system as described herein, the image sidesurface of the first lens element (lens 1) may be flat/plano (e.g., lens1 may be plano-convex), and the image side surface of lens 1 may beat/in contact with the object side surface of the light folding prism toeffectively form a single combined unit or element. The lens 1 and prismelements may be composed of the same type of material (e.g., a plasticmaterial) or of different types of materials. In some embodiments, thelens 1 and prism elements may be cemented. Alternatively, the lens 1 andprism elements may be composed of the same type of material (e.g., aplastic material), and may be molded as a single combined unit orelement. However, while not shown in the example Figures, in someembodiments the image side surface of lens 1 may be convex, concave, orflat-plano, and lens 1 and the folding element (prism) may beair-spaced.

Example Lens System 210

FIGS. 2A and 2B show a camera 200 that includes an example embodiment ofa compact folded lens system 210 that operates at F/2.4, with 31° fullFOV. Camera 200 includes a 5.04 mm diagonal photosensor 220. Lens system210 includes four lens elements with refractive power and a foldingelement such as a prism, in order from the object side to the image sideof the lens system: a first lens element 201 with positive refractivepower, a folding element 240 such as a prism to fold the optical axisfrom AX1 to AX2, a second lens element 202 with negative refractivepower, a third lens element 203 with refractive power, and a fourth lenselement 204 with refractive power. An aperture stop 230 may be locatedbetween the object side of the lens system 210 and the folding element240, for example at or near the object side surface of lens element 201,for controlling the brightness of the optical system. In someembodiments, the lens system 210 or camera 200 includes an IR filter 250to reduce or eliminate interference of environmental noises on thephotosensor 220.

Tables 1-5 correspond to an embodiment of a lens system 210 asillustrated in FIGS. 2A and 2B, and provide example values for variousoptical and physical parameters of the lens system 210 and camera 200 ofFIGS. 2A and 2B. The effective focal length (EFL) of the lens system 210is 9 mm. Given the EFL and photosensor size, the 35 mm equivalent focallength of the camera 210 may be 77 mm. In some embodiments, the camera200/lens system 210 has the capability of autofocusing from 700 mm toInfinity conjugates.

As shown in FIGS. 2A-2B, in some embodiments the photosensor 220 may bemoved on one or more axes relative to the lens system 210 to adjustfocus of the camera 200. FIG. 2A corresponds to the camera 200 focusedat a first position (infinity conjugate), and FIG. 2B corresponds to thecamera 200 focused at a second position (700 mm in FIG. 2B). While thefocus positions are shown as examples, note that the camera 200 may befocused at other positions in some embodiments.

The modulation transfer functions (MTFs) for lens system 210 whenfocused at Infinity and Macro (500 mm) conjugates, at all fields andboth conjugates, are close to diffraction limited; the lens system 210provides good contrast for high-resolution imaging. At both conjugates,on-axis and off-axis aberrations for lens system 210 are well balancedacross the FOV. At both conjugates, optical distortion across the FOV iscontrolled within 2%, while field curvature and astigmatism are wellbalanced across the FOV.

In some embodiments, Z-height of the example lens system 210, as definedfrom the front vertex of lens element 201 to the rear vertex of thefolding element 240, may be 4.85 mm. The lens system 210 is able to fitinto a wide variety of portable electronic devices including but notlimited to smart phones and tablets.

Example Lens System 310

FIG. 3 shows a camera 300 that includes an example embodiment of acompact folded lens system 310 that operates at F/2.4, with 28.1° fullFOV. Camera 300 includes a 5.04 mm diagonal photosensor 320. Lens system310 includes four lens elements with refractive power and a foldingelement such as a prism, in order from the object side to the image sideof the lens system: a first lens element 301 with positive refractivepower, a folding element 340 such as a prism to fold the optical axisfrom AX1 to AX2, a second lens element 302 with negative refractivepower, a third lens element 303 with refractive power, and a fourth lenselement 304 with refractive power. An aperture stop 330 may be locatedbetween the object side of the lens system 310 and the folding element340, for example at or near the object side surface of lens element 301,for controlling the brightness of the optical system. In someembodiments, the lens system 310 or camera 300 includes an IR filter 350to reduce or eliminate interference of environmental noises on thephotosensor 320.

Tables 6-9 correspond to an embodiment of a lens system 310 asillustrated in FIG. 3, and provide example values for various opticaland physical parameters of the lens system 310 and camera 300 of FIG. 3.The effective focal length (EFL) of the lens system 310 is 10 mm. Giventhe EFL and photosensor size, the 35 mm equivalent focal length of thecamera 310 may be 86 mm. While not shown in FIG. 3, in some embodiments,the camera 300/lens system 310 has the capability of autofocusing fromMacro to Infinity conjugates.

The modulation transfer function (MTF) for lens system 310 is close todiffraction limited; the lens system 310 provides good contrast forhigh-resolution imaging. On-axis and off-axis aberrations for lenssystem 310 are well balanced across the FOV. Optical distortion acrossthe FOV is controlled within 2%, while field curvature and astigmatismare well balanced across the FOV.

In some embodiments, Z-height of the example lens system 310, as definedfrom the front vertex of lens element 301 to the rear vertex of thefolding element 340, may be 5.35 mm. The lens system 310 is able to fitinto a wide variety of portable electronic devices including but notlimited to smart phones and tablets.

Example Lens System 410

FIG. 4 shows a camera 400 that includes an example embodiment of acompact folded lens system 410 that operates at F/2.2, with 42.2° fullFOV. Camera 400 includes a 5.04 mm diagonal photosensor 420. Lens system410 includes four lens elements with refractive power and a foldingelement such as a prism, in order from the object side to the image sideof the lens system: a first lens element 401 with positive refractivepower, a folding element 440 such as a prism to fold the optical axisfrom AX1 to AX2, a second lens element 402 with negative refractivepower, a third lens element 403 with refractive power, and a fourth lenselement 404 with refractive power. An aperture stop 430 may be locatedbetween the object side of the lens system 410 and the folding element440, for example at or near the object side surface of lens element 401,for controlling the brightness of the optical system. In someembodiments, the lens system 410 or camera 400 includes an IR filter 450to reduce or eliminate interference of environmental noises on thephotosensor 420.

Tables 10-13 correspond to an embodiment of a lens system 410 asillustrated in FIG. 4, and provide example values for various opticaland physical parameters of the lens system 410 and camera 400 of FIG. 4.The effective focal length (EFL) of the lens system 410 is 6.6 mm. Giventhe EFL and photosensor size, the 35 mm equivalent focal length of thecamera 410 may be 57 mm. While not shown in FIG. 4, in some embodiments,the camera 400/lens system 410 has the capability of autofocusing fromMacro to Infinity conjugates.

The modulation transfer function (MTF) for lens system 410 is higherthan 0.6 at 125 lp/mm and higher than 0.3 at 250 lp/mm; the lens system410 provides good contrast for high-resolution imaging. On-axis andoff-axis aberrations for lens system 410 are well balanced across theFOV. Optical distortion across the FOV is controlled within 2%, whilefield curvature and astigmatism are well balanced across the FOV.

In some embodiments, Z-height of the example lens system 410, as definedfrom the front vertex of lens element 401 to the rear vertex of thefolding element 440, may be 4.4 mm. The lens system 410 is able to fitinto a wide variety of portable electronic devices including but notlimited to smart phones and tablets.

Example Lens System 510

FIG. 5 shows a camera 500 that includes an example embodiment of acompact folded lens system 510 that operates at F/2.6, with 23.7° fullFOV. Camera 500 includes a 5.04 mm diagonal photosensor 520. Lens system510 includes four lens elements with refractive power and a foldingelement such as a prism, in order from the object side to the image sideof the lens system: a first lens element 501 with positive refractivepower, a folding element 540 such as a prism to fold the optical axisfrom AX1 to AX2, a second lens element 502 with negative refractivepower, a third lens element 503 with refractive power, and a fourth lenselement 504 with refractive power. An aperture stop 530 may be locatedbetween the object side of the lens system 510 and the folding element540, for example at or near the object side surface of lens element 501,for controlling the brightness of the optical system. In someembodiments, the lens system 510 or camera 500 includes an IR filter 550to reduce or eliminate interference of environmental noises on thephotosensor 520.

Tables 14-17 correspond to an embodiment of a lens system 510 asillustrated in FIG. 5, and provide example values for various opticaland physical parameters of the lens system 510 and camera 500 of FIG. 5.The effective focal length (EFL) of the lens system 510 is 12 mm. Giventhe EFL and photosensor size, the 35 mm equivalent focal length of thecamera 510 may be 103 mm. While not shown in FIG. 5, in someembodiments, the camera 500/lens system 510 has the capability ofautofocusing from Macro to Infinity conjugates.

The modulation transfer function (MTF) for lens system 510 is close todiffraction limited; the lens system 510 provides good contrast forhigh-resolution imaging. On-axis and off-axis aberrations for lenssystem 510 are well balanced across the FOV. Optical distortion acrossthe FOV is controlled within 2%, while field curvature and astigmatismare well balanced across the FOV.

In some embodiments, Z-height of the example lens system 510, as definedfrom the front vertex of lens element 501 to the rear vertex of thefolding element 540, may be 5.85 mm. The lens system 510 is able to fitinto a wide variety of portable electronic devices including but notlimited to smart phones and tablets.

Example Lens System 610

FIG. 6 shows a camera 600 that includes an example embodiment of acompact folded lens system 610 that operates at F/2.4, with 31.2° fullFOV. Camera 600 includes a 4.54 mm diagonal photosensor 620. Lens system610 includes four lens elements with refractive power and a foldingelement such as a prism, in order from the object side to the image sideof the lens system: a first lens element 601 with positive refractivepower, a folding element 640 such as a prism to fold the optical axisfrom AX1 to AX2, a second lens element 602 with negative refractivepower, a third lens element 603 with refractive power, and a fourth lenselement 604 with refractive power. An aperture stop 630 may be locatedbetween the object side of the lens system 610 and the folding element640, for example at or near the object side surface of lens element 601,for controlling the brightness of the optical system. In someembodiments, the lens system 610 or camera 600 includes an IR filter 650to reduce or eliminate interference of environmental noises on thephotosensor 620.

Tables 18-21 correspond to an embodiment of a lens system 610 asillustrated in FIG. 6, and provide example values for various opticaland physical parameters of the lens system 610 and camera 600 of FIG. 6.The effective focal length (EFL) of the lens system 610 is 8.1 mm. Giventhe EFL and photosensor size, the 35 mm equivalent focal length of thecamera 610 may be 77 mm. While not shown in FIG. 6, in some embodiments,the camera 600/lens system 610 has the capability of autofocusing fromMacro to Infinity conjugates.

The modulation transfer function (MTF) for lens system 610 is close todiffraction limited; the lens system 610 provides good contrast forhigh-resolution imaging. On-axis and off-axis aberrations for lenssystem 610 are well balanced across the FOV. Optical distortion acrossthe FOV is controlled within 2%, while field curvature and astigmatismare well balanced across the FOV.

In some embodiments, Z-height of the example lens system 610, as definedfrom the front vertex of lens element 601 to the rear vertex of thefolding element 640, may be 4.45 mm. The lens system 610 is able to fitinto a wide variety of portable electronic devices including but notlimited to smart phones and tablets.

Example Lens System 710

FIG. 7 shows a camera 700 that includes an example embodiment of acompact folded lens system 710 that operates at F/3, with 20.4° fullFOV. Camera 700 includes a 5.04 mm diagonal photosensor 720. Lens system710 includes four lens elements with refractive power and a foldingelement such as a prism, in order from the object side to the image sideof the lens system: a first lens element 701 with positive refractivepower, a folding element 740 such as a prism to fold the optical axisfrom AX1 to AX2, a second lens element 702 with negative refractivepower, a third lens element 703 with refractive power, and a fourth lenselement 704 with refractive power. An aperture stop 730 may be locatedbetween the object side of the lens system 710 and the folding element740, for example at or near the object side surface of lens element 701,for controlling the brightness of the optical system. In someembodiments, the lens system 710 or camera 700 includes an IR filter 750to reduce or eliminate interference of environmental noises on thephotosensor 720.

Tables 22-25 correspond to an embodiment of a lens system 710 asillustrated in FIG. 7, and provide example values for various opticaland physical parameters of the lens system 710 and camera 700 of FIG. 7.The effective focal length (EFL) of the lens system 70 is 14 mm. Giventhe EFL and photosensor size, the 35 mm equivalent focal length of thecamera 710 may be 120 mm. While not shown in FIG. 7, in someembodiments, the camera 700/lens system 710 has the capability ofautofocusing from Macro to Infinity conjugates.

The modulation transfer function (MTF) for lens system 710 is close todiffraction limited; the lens system 710 provides good contrast forhigh-resolution imaging. On-axis and off-axis aberrations for lenssystem 710 are well balanced across the FOV. Optical distortion acrossthe FOV is controlled within 2%, while field curvature and astigmatismare well balanced across the FOV.

In some embodiments, Z-height of the example lens system 710, as definedfrom the front vertex of lens element 701 to the rear vertex of thefolding element 740, may be 5.75 mm. The lens system 710 is able to fitinto a wide variety of portable electronic devices including but notlimited to smart phones and tablets.

Example Lens System Tables

The following Tables provide example values for various optical andphysical parameters of the example embodiments of the lens systems andcameras as described in reference to FIGS. 2A through 7. Tables 1-5correspond to an example embodiment of a lens system 210 as illustratedin FIGS. 2A and 2B. Note that Tables 1-5 may also correspond to anexample embodiment of a lens system 110 as illustrated in FIG. 1. Tables6-9 correspond to an example embodiment of a lens system 310 asillustrated in FIG. 3. Tables 10-13 correspond to an example embodimentof a lens system 410 as illustrated in FIG. 4. Tables 14-17 correspondto an example embodiment of a lens system 510 as illustrated in FIG. 5.Tables 18-21 correspond to an example embodiment of a lens system 610 asillustrated in FIG. 6. Tables 22-25 correspond to an example embodimentof a lens system 710 as illustrated in FIG. 7.

In the Tables, all dimensions are in millimeters (mm) unless otherwisespecified. L1, L2, L3, and L4 stand for refractive lenses 1, 2, 3, and4, respectively. “S#” stands for surface number. A positive radiusindicates that the center of curvature is to the right (object side) ofthe surface. A negative radius indicates that the center of curvature isto the left (image side) of the surface. “INF” stands for infinity (asused in optics). The thickness (or separation) is the axial distance tothe next surface. FNO stands for F-number of the lens system. FOV standsfor full field of view. f_(35 mm) is the 35 mm equivalent focal lengthof the lens system. V₁ is the Abbe number of the first lens element, andV₂ is the Abbe number of the second lens element. Both f and EFL standfor effective focal length of the lens system, f1 stands for focallength of the first lens element, and f2 stands for focal length of thesecond lens element. R4 f is radius of curvature of the object-sidesurface of lens 4, and R4 r is radius of curvature of the image sidesurface of lens 4. Z stands for Z-height of the lens system as definedfrom the front (image side) vertex of the lens system to the rear vertexof the folding element (e.g., prism), as shown in FIG. 1. REFLrepresents a reflective surface.

For the materials of the lens elements and IR filter, a refractive indexN_(d) at the helium d-line wavelength is provided, as well as an Abbenumber V_(d) relative to the d-line and the C- and F-lines of hydrogen.The Abbe number, V_(d), may be defined by the equation:

V _(d)=(N _(d−)1)/(N _(F) −N _(C)),

where N_(F) and N_(C) are the refractive index values of the material atthe F and C lines of hydrogen, respectively.

Referring to the Tables of aspheric coefficients (Tables, 2A-2B, 7A-7B,11A-11B, 15A-15B, 19A-19B, and 23A-23B), the aspheric equationdescribing an aspherical surface may be given by:

Z=(cr ²/(1+sqrt[1−(1+K)c ² r ²]))+A ₄ r ⁴ +A ₆ r ⁶ +A ₈ r ⁸ +A ₁₀ r ¹⁰+A ₁₂ R ¹² +A ₁₄ r ¹⁴ +A ₁₆ r ¹⁶ +A ₁₈ r ¹⁸ +A ₂₀ r ²⁰

where Z is the sag of surface parallel to the z-axis (the z-axis and theoptical axis are coincident in these example embodiments), r is theradial distance from the vertex, c is the curvature at the pole orvertex of the surface (the reciprocal of the radius of curvature of thesurface), K is the conic constant, and A₄-A₂₀ are the asphericcoefficients. In the Tables, “E” denotes the exponential notation(powers of 10).

Note that the values given in the following Tables for the variousparameters in the various embodiments of the lens system are given byway of example and are not intended to be limiting. For example, one ormore of the parameters for one or more of the surfaces of one or more ofthe lens elements in the example embodiments, as well as parameters forthe materials of which the elements are composed, may be given differentvalues while still providing similar performance for the lens system. Inparticular, note that some values in the Tables may be scaled up or downfor larger or smaller implementations of a camera using an embodiment ofa lens system as described herein.

Further note that surface numbers (S#) of the elements in the variousembodiments of the lens system as shown in the Tables are listed from afirst surface 0 at the object plane to a last surface at the imageplane/photosensor surface. FIG. 8 illustrates numbering of the surfacesas used in the Tables. As shown in FIG. 8, in some embodiments of acompact folded lens system as described herein, the image side surfaceof the first lens element (lens 1) may be flat/plano (e.g., lens 1 maybe plano-convex), and the image side surface of lens 1 may be at/incontact with the object side surface of the light folding prism 40 toeffectively form a single combined unit or element. In theseembodiments, the image side surface of lens 1 and the object sidesurface of the prism 40 form and are designated as a single surface, andthe surfaces are numbered as illustrated in FIG. 8:

S0—Object plane

S1—Aperture stop

S2—Lens 1, object side surface

S3—Prism 40, image side surface

S4—Prism 40, reflective surface

S5—Prism, object side surface

S6—Lens 2, object side surface

S7—Lens 2, image side surface

S8—Lens 3, object side surface

S9—Lens 3, image side surface

S10—Lens 4, object side surface

S11—Lens 4, image side surface

S12—IR filter 50, object side surface

S13—IR filter 50, image side surface

S14—Photosensor 20, image plane

TABLE 1 Lens system 210 Fno = 2.4, EFL = 9 mm, FOV = 31°, f_(35 mm) = 77mm Thickness or Refractive Abbe Element Surface (S#) Radius (mm)separation (mm) Index N_(d) Number V_(d) Object 0 INF INF **1 Stop 1 INF−0.4253 L1 *2  4.1390  0.7090 1.513 56.6 Prism 3 INF  2.0645 1.755 27.6Decenter (1) 4 INF −2.0645 REFL Bend (1) 5 INF −0.1000 L2 *6 −6.2180−0.7980 1.651 21.5 *7 −2.6800 −1.4810 L3 *8 −3.3300 −1.5000 1.545 55.9*9 −6.4860 −0.9520 L4 *10 −3.5860 −0.9080 1.545 55.9 *11 −2.7010 −1.0750IR filter 12 INF −0.2100 1.517 64.2 13 INF −0.1000 14 INF 0 **2*Annotates aspheric surfaces (aspheric coefficients given in Tables2A-2B) **Annotates zoom parameters (values given in Table 4)

TABLE 2A Aspheric Coefficients (Lens System 210) Surface (S#) S2 S6 S7S8 S9 K 0 0 0 0 0 A4 1.075350E−04   2.439694E−02 3.791761E−023.637417E−03   8.231862E−03 A6 1.207931E−05 −1.069533E−03−2.010331E−03   3.931192E−04 −3.641826E−03 A8 0.000000E+00 −3.872791E−056.218673E−05 1.643827E−05   8.834411E−04 A10 0.000000E+00 −7.475811E−061.687762E−05 8.500108E−06 −1.430153E−04 A12 0.000000E+00   4.716422E−061.483912E−06 0.000000E+00   1.552517E−05 A14 0.000000E+00   0.000000E+000.000000E+00 0.000000E+00 −1.067392E−06 A16 0.000000E+00   0.000000E+000.000000E+00 0.000000E+00   0.000000E+00 A18  0.00000E+00    0.00000E+00 0.00000E+00  0.00000E+00    0.00000E+00 A20  0.00000E+00    0.00000E+00 0.00000E+00  0.00000E+00    0.00000E+00

TABLE 2B Aspheric Coefficients (Lens System 210) Surface (S#) S10 S11 K0 0 A4 4.424514E−02 4.864336E−02 A6 −2.698281E−03   −3.955844E−03   A8−2.784513E−04   2.948393E−04 A10 1.678942E−05 −1.358085E−05   A120.000000E+00 −1.191172E−06   A14 0.000000E+00 3.605321E−07 A16  0.00E+00   0.00E+00 A18  0.00000E+00  0.00000E+00 A20  0.00000E+00 0.00000E+00

TABLE 3 Decentering Constants (Lens System 210) Decenter X Y ZAlpha(deg) Beta(deg) Gamma (deg) D(1) and 0 0 0 45 0 0 Bend (1)

TABLE 4 Zoom Parameters (Lens System 210) **Zoom parameters Position-1Position-2 **1 Infinity     700 mm **2 0.000 −0.115 mm

TABLE 5 Optical Definitions (Lens system 210) EFL   9 mm V₁ 56.6 FNO 2.4V₂ 21.5 FOV 31° |f/f1| 0.64 f_(35 mm)   77 mm |f/f2| 1.14 Z 4.85 mm |R4f− R4r|/|R4f + R4r| 0.14

TABLE 6 Lens system 310 Fno = 2.4, EFL = 10 mm, FOV = 28.1°, f_(35 mm) =86 mm Thickness or Refractive Abbe Element Surface (S#) Radius (mm)separation (mm) Index N_(d) Number V_(d) Object 0 INF INF Stop 1 INF−0.5000 L1 *2  4.3690 0.7780 1.513 56.6 Prism 3 INF 2.2830 1.755 27.6Decenter (1) 4 INF −2.2830 REFL Bend (1) 5 INF −0.0500 L2 *6 −6.3250−0.6420 1.651 21.5 *7 −2.7690 −1.3860 L3 *8 −3.2130 −1.4870 1.545 55.9*9 −8.0790 −0.9960 L4 *10 −8.9340 −0.8610 1.545 55.9 *11 −3.9490 −1.5500IR filter 12 INF −0.2100 1.517 64.2 13 INF −0.1000 14 INF 0.0000*Annotates aspheric surfaces (aspheric coefficients given in Tables7A-7B)

TABLE 7A Aspheric Coefficients (Lens System 310) Surface (S#) S2 S6 S7S8 S9 K 0 0 0 0 0 A4 −1.185992E−04  2.418232E−02 3.555325E−021.824810E−03 2.536181E−03 A6 −4.993100E−06  −1.831987E−03 −2.448378E−03  5.056339E−04 −6.020578E−04  A8 0.000000E+00−1.015260E−05  1.020881E−04 −7.150725E−07  1.855878E−04 A10 0.000000E+009.750139E−06 1.063693E−05 2.004868E−06 1.754149E−05 A12 0.000000E+000.000000E+00 0.000000E+00 0.000000E+00 −3.933255E−06  A14 0.000000E+000.000000E+00 0.000000E+00 0.000000E+00 1.541867E−07 A16 0.000000E+000.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 A18 0.000000E+000.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 A20 0.000000E+000.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00

TABLE 7B Aspheric Coefficients (Lens System 310) Surface (S#) S10 S11 K0 0 A4 4.430967E−02 4.249250E−02 A6 −1.271181E−03  −3.916083E−03  A8−2.677368E−04  1.401346E−04 A10 1.277254E−05 −4.477309E−06  A12−3.214856E−07  3.308677E−08 A14 0.000000E+00 0.000000E+00 A160.000000E+00 0.000000E+00 A18 0.000000E+00 0.000000E+00 A20 0.000000E+000.000000E+00

TABLE 8 Decentering Constants (Lens System 310) Decenter X Y ZAlpha(deg) Beta(deg) Gamma (deg) D(1) and 0 0 0 45 0 0 Bend (1)

TABLE 9 Optical Definitions (Lens system 310) EFL 10 mm V₁ 56.6 FNO  2.4V₂ 21.5 FOV 28.1° |f/f1| 0.67 f_(35 mm) 86 mm |f/f2| 1.24 Z 5.35 mm |R4f − R4r|/|R4f + R4r| 0.39

TABLE 10 Lens system 410 Fno = 2.2, EFL = 6.6 mm, FOV = 42.2°, f_(35 mm)= 57 mm Thickness or Refractive Abbe Element Surface (S#) Radius (mm)separation (mm) Index N_(d) Number V_(d) Object 0 INF INF Stop 1 INF−0.2820 L1 *2 3.2470 0.6170 1.513 56.6 Prism 3 INF 1.8725 1.755 27.6Decenter (1) 4 INF −1.8725 REFL Bend (1) 5 INF −0.0500 L2 *6 −5.5010−0.6170 1.661 20.4 *7 −2.2820 −0.3780 L3 *8 −5.3630 −0.8000 1.545 55.9*9 4.9180 −1.0650 L4 *10 −11.8660 −0.5000 1.545 55.9 *11 −2.5020 −0.8070IR filter 12 INF −0.2100 1.517 64.2 13 INF −0.1000 14 INF 0.0000*Annotates aspheric surfaces (aspheric coefficients given in Tables11A-11B)

TABLE 11A Aspheric Coefficients (Lens System 410) Surface (S#) S2 S6 S7S8 S9 K 0 0 0 0 0 A4 −1.185992E−04  2.418232E−02 3.555325E−021.824810E−03 2.536181E−03 A6 −4.993100E−06  −1.831987E−03 −2.448378E−03  5.056339E−04 −6.020578E−04  A8 0.000000E+00−1.015260E−05  1.020881E−04 −7.150725E−07  1.855878E−04 A10 0.000000E+009.750139E−06 1.063693E−05 2.004868E−06 1.754149E−05 A12 0.000000E+000.000000E+00 0.000000E+00 0.000000E+00 −3.933255E−06  A14 0.000000E+000.000000E+00 0.000000E+00 0.000000E+00 1.541867E−07 A16 0.000000E+000.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 A18 0.000000E+000.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 A20 0.000000E+000.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00

TABLE 11B Aspheric Coefficients (Lens System 410) Surface (S#) S10 S11 K0 0 A4 4.430967E−02 4.249250E−02 A6 −1.271181E−03  −3.916083E−03  A8−2.677368E−04  1.401346E−04 A10 1.277254E−05 −4.477309E−06  A12−3.214856E−07  3.308677E−08 A14 0.000000E+00 0.000000E+00 A160.000000E+00 0.000000E+00 A18 0.000000E+00 0.000000E+00 A20 0.000000E+000.000000E+00

TABLE 12 Decentering Constants (Lens System 410) Decenter X Y ZAlpha(deg) Beta(deg) Gamma (deg) D(1) and 0 0 0 45 0 0 Bend (1)

TABLE 13 Optical Definitions (Lens system 410) EFL 6.6 mm V₁ 56.6 FNO 2.2 V₂ 20.4 FOV 42.2° |f/f1| 0.59 f_(35 mm)  57 mm |f/f2| 1.04 Z 4.4 mm|R4f − R4r|/|R4f + R4r| 0.65

TABLE 14 Lens system 510 Fno = 2.6, EFL = 12 mm, FOV = 23.7°, f_(35 mm)= 103 mm Thickness or Refractive Abbe Element Surface (S#) Radius (mm)separation (mm) Index N_(d) Number V_(d) Object 0 INF INF Stop 1 INF−0.5376 L1 *2  4.9890 0.8240 1.513 56.6 Prism 3 INF 2.5020 1.755 27.6Decenter (1) 4 INF −2.5020 REFL Bend (1) 5 INF −0.0500 L2 *6 −5.9940−0.5980 1.651 21.5 *7 −3.0150 −2.0714 L3 *8 −3.2000 −1.5670 1.545 55.9*9 −4.3040 −1.0600 L4 *10 −5.6600 −0.6990 1.545 55.9 *11 −4.2910 −2.3200IR filter 12 INF −0.2100 1.517 64.2 13 INF −0.1000 14 INF 0.0000*Annotates aspheric surfaces (aspheric coefficients given in Tables15A-15B)

TABLE 15A Aspheric Coefficients (Lens System 510) Surface (S#) S2 S6 S7S8 S9 K 0 0 0 0 0 A4 −6.582527E−05  2.037533E−02 2.884337E−021.642463E−03 3.926273E−03 A6 2.046512E−06 −1.110012E−03  −1.366167E−03 1.480820E−04 −2.248217E−03  A8 0.000000E+00 0.000000E+00 3.673243E−057.238769E−05 6.422383E−04 A10 0.000000E+00 0.000000E+00 2.273830E−06−1.946842E−06  −8.971135E−05  A12 0.000000E+00 0.000000E+00 0.000000E+000.000000E+00 1.268152E−05 A14 0.000000E+00 0.000000E+00 0.000000E+000.000000E+00 −1.218277E−06  A16 0.000000E+00 0.000000E+00 0.000000E+000.000000E+00 0.000000E+00 A18 0.000000E+00 0.000000E+00 0.000000E+000.000000E+00 0.000000E+00 A20 0.000000E+00 0.000000E+00 0.000000E+000.000000E+00 0.000000E+00

TABLE 15B Aspheric Coefficients (Lens System 510) Surface (S#) S10 S11 K0 0 A4 4.679289E−02 4.674529E−02 A6 −3.481463E−03  −5.658225E−03  A82.305817E−04 6.688362E−04 A10 −1.991886E−05  −7.402455E−05  A12−1.788224E−06  3.598719E−06 A14 0.000000E+00 0.000000E+00 A160.000000E+00 0.000000E+00 A18 0.000000E+00 0.000000E+00 A20 0.000000E+000.000000E+00

TABLE 16 Decentering Constants (Lens System 510) Decenter X Y ZAlpha(deg) Beta(deg) Gamma (deg) D(1) and 0 0 0 45 0 0 Bend (1)

TABLE 17 Optical Definitions (Lens system 510) EFL  12 mm V₁ 56.6 FNO 2.6 V₂ 21.5 FOV 23.7° |f/f1| 0.70 f_(35 mm) 103 mm |f/f2| 1.20 Z 5.85mm  |R4f − R4r|/|R4f + R4r| 0.14

TABLE 18 Lens system 610 Fno = 2.4, EFL = 8.1 mm, FOV = 31.2°, f_(35 mm)= 77 mm Thickness or Refractive Abbe Element Surface (S#) Radius (mm)separation (mm) Index N_(d) Number V_(d) Object 0 INF INF Stop 1 INF−0.3656 L1 *2 3.7650 0.6490 1.513 56.6 Prism 3 INF 1.8980 1.755 27.6Decenter (1) 4 INF −1.8980 REFL Bend (1) 5 INF −0.1000 L2 *6 −5.7300−0.5780 1.651 21.5 *7 −2.4180 −1.0040 L3 *8 −2.9820 −1.3460 1.545 55.9*9 −10.2080 −0.7800 L4 *10 −4.7340 −0.8650 1.545 55.9 *11 −2.6520−1.2270 IR filter 12 INF −0.2100 1.517 64.2 13 INF −0.1000 14 INF 0.0000*Annotates aspheric surfaces (aspheric coefficients given in Tables19A-19B)

TABLE 19A Aspheric Coefficients (Lens System 610) Surface (S#) S2 S6 S7S8 S9 K 0 0 0 0 0 A4 −2.360340E−04  3.402370E−02 5.016939E−021.819421E−03 7.779075E−03 A6 −2.111947E−05  −3.386172E−03 −4.162309E−03  9.935049E−04 −4.046032E−03  A8 0.000000E+00 7.735521E−062.891013E−04 −3.703260E−05  1.280125E−03 A10 0.000000E+00 1.696235E−051.413009E−05 1.094440E−05 −2.265344E−04  A12 0.000000E+00 0.000000E+000.000000E+00 0.000000E+00 3.220049E−05 A14 0.000000E+00 0.000000E+000.000000E+00 0.000000E+00 −3.230947E−06  A16 0.000000E+00 0.000000E+000.000000E+00 0.000000E+00 0.000000E+00 A18 0.000000E+00 0.000000E+000.000000E+00 0.000000E+00 0.000000E+00 A20 0.000000E+00 0.000000E+000.000000E+00 0.000000E+00 0.000000E+00

TABLE 19B Aspheric Coefficients (Lens System 610) Surface (S#) S10 S11 K0 0 A4 6.462879E−02 6.507028E−02 A6 −3.617937E−03  −6.851818E−03  A8−4.038654E−04  4.452252E−04 A10 −1.039311E−05  −5.908594E−06  A120.000000E+00 0.000000E+00 A14 0.000000E+00 0.000000E+00 A16 0.000000E+000.000000E+00 A18 0.000000E+00 0.000000E+00 A20 0.000000E+00 0.000000E+00

TABLE 20 Decentering Constants (Lens System 610) Decenter X Y ZAlpha(deg) Beta(deg) Gamma (deg) D(1) and 0 0 0 45 0 0 Bend (1)

TABLE 21 Optical Definitions (Lens system 610) EFL 8.1 mm V₁ 56.6 FNO 2.4 V₂ 21.5 FOV 31.2° |f/f1| 0.63 f_(35 mm)  77 mm |f/f2| 1.18 Z 4.45mm  |R4f − R4r|/|R4f + R4r| 0.28

TABLE 22 Lens system 710 Fno = 3.0, EFL = 14 mm, FOV = 20.4°, f_(35 mm)= 120 mm Thickness or Refractive Abbe Element Surface (S#) Radius (mm)separation (mm) Index N_(d) Number V_(d) Object 0 INF INF Stop 1 INF−0.5231 L1 *2  5.2200 0.8040 1.513 56.6 Prism 3 INF 2.4750 1.755 27.6Decenter (1) 4 INF −2.4750 REFL Bend (1) 5 INF −0.0500 L2 *6 −5.6950−0.5640 1.651 21.5 *7 −3.0700 −2.4640 L3 *8 −3.0760 −1.4990 1.545 55.9*9 −3.5620 −1.4890 L4 *10 12.6070 −0.7620 1.545 55.9 *11 26.1350 −2.7660IR filter 12 INF −0.2100 1.517 64.2 13 INF −0.1000 14 INF 0.0000*Annotates aspheric surfaces (aspheric coefficients given in Tables23A-23B)

TABLE 23A Aspheric Coefficients (Lens System 710) Surface (S#) S2 S6 S7S8 S9 K 0 0 0 0 0 A4 −2.745195E−05  2.036332E−02 2.867198E−022.551997E−03 2.400665E−04 A6 4.097874E−06 −1.192201E−03  −1.661519E−03 3.767858E−04 1.776187E−05 A8 0.000000E+00 −1.332816E−05  5.296870E−05−7.901097E−06  −1.579635E−05  A10 0.000000E+00 6.595165E−06 7.881696E−065.689791E−06 1.479408E−05 A12 0.000000E+00 0.000000E+00 0.000000E+000.000000E+00 3.285398E−07 A14 0.000000E+00 0.000000E+00 0.000000E+000.000000E+00 −6.354672E−08  A16 0.000000E+00 0.000000E+00 0.000000E+000.000000E+00 0.000000E+00 A18 0.000000E+00 0.000000E+00 0.000000E+000.000000E+00 0.000000E+00 A20 0.000000E+00 0.000000E+00 0.000000E+000.000000E+00 0.000000E+00

TABLE 23B Aspheric Coefficients (Lens System 710) Surface (S#) S10 S11 K0 0 A4 3.006845E−02 2.597292E−02 A6 −4.706480E−04  −1.734303E−03  A8−5.268048E−06  1.066114E−04 A10 1.030203E−05 1.158703E−06 A120.000000E+00 −5.999168E−07  A14 0.000000E+00 0.000000E+00 A160.000000E+00 0.000000E+00 A18 0.000000E+00 0.000000E+00 A20 0.000000E+000.000000E+00

TABLE 24 Decentering Constants (Lens System 710) Decenter X Y ZAlpha(deg) Beta(deg) Gamma (deg) D(1) and 0 0 0 45 0 0 Bend (1)

TABLE 25 Optical Definitions (Lens system 710) EFL  14 mm V₁ 56.6 FNO 3.0 V₂ 21.5 FOV 20.4° |f/f1| 0.78 f_(35 mm) 120 mm |f/f2| 1.26 Z 5.75mm  |R4f − R4r|/|R4f + R4r| 0.35

Example Flowchart

FIG. 9 is a high-level flowchart of a method for capturing images usinga camera with a lens system that includes four lens elements and afolding element as illustrated in FIGS. 1 through 8, according to someembodiments. As indicated at 2500, light from an object field in frontof the camera is received at a first lens element of the camera throughan aperture stop. In some embodiments, the aperture stop may be locatedat the first lens element and behind the front vertex of the lenssystem. As indicated at 2502, the first lens element refracts the lighton a first axis AX1 to a light folding element such as a prism. Asindicated at 2504, the light is redirected by the folding element to asecond lens element on a second axis AX2. As indicated at 2506, thelight is then refracted by the second lens element to a third lenselement on the second axis AX2. As indicated at 2508, the light is thenrefracted by the third lens element to a fourth lens element on thesecond axis AX2. As indicated at 2510, the light is then refracted bythe fourth lens element to form an image at an image plane at or nearthe surface of a photosensor. As indicated at 2514, the image iscaptured by the photosensor. While not shown, in some embodiments, thelight may pass through an infrared filter that may for example belocated between the fourth lens element and the photosensor.

In some embodiments, the elements referred to in FIG. 9 may beconfigured as illustrated in FIGS. 1 through 7. However, note thatvariations on the example as given in the Figures are possible whileachieving similar optical results.

Example Computing Device

FIG. 10 illustrates an example computing device, referred to as computersystem 4000, that may include or host embodiments of the camera asillustrated in FIGS. 1 through 9. In addition, computer system 4000 mayimplement methods for controlling operations of the camera and/or forperforming image processing of images captured with the camera. Indifferent embodiments, computer system 4000 may be any of various typesof devices, including, but not limited to, a personal computer system,desktop computer, laptop, notebook, tablet or pad device, slate, ornetbook computer, mainframe computer system, handheld computer,workstation, network computer, a camera, a set top box, a mobile device,a mobile multipurpose device, a wireless phone, a smartphone, a consumerdevice, video game console, handheld video game device, applicationserver, storage device, a television, a video recording device, or ingeneral any type of computing or electronic device.

In the illustrated embodiment, computer system 4000 includes one or moreprocessors 4010 coupled to a system memory 4020 via an input/output(I/O) interface 4030. Computer system 4000 further includes a networkinterface 4040 coupled to I/O interface 4030, and one or moreinput/output devices 4050, such as cursor control device 4060, keyboard4070, and display(s) 4080. Computer system 4000 may also include one ormore cameras 4090, for example one or more cameras as described abovewith respect to FIGS. 1 through 9, which may also be coupled to I/Ointerface 4030, or one or more cameras as described above with respectto FIGS. 1 through 9 along with one or more other cameras such aswide-field cameras.

In various embodiments, computer system 4000 may be a uniprocessorsystem including one processor 4010, or a multiprocessor systemincluding several processors 4010 (e.g., two, four, eight, or anothersuitable number). Processors 4010 may be any suitable processor capableof executing instructions. For example, in various embodimentsprocessors 4010 may be general-purpose or embedded processorsimplementing any of a variety of instruction set architectures (ISAs),such as the x86, PowerPC, SPARC, or MIPS ISAs, or any other suitableISA. In multiprocessor systems, each of processors 4010 may commonly,but not necessarily, implement the same ISA.

System memory 4020 may be configured to store program instructions 4022and/or data 4032 accessible by processor 4010. In various embodiments,system memory 4020 may be implemented using any suitable memorytechnology, such as static random access memory (SRAM), synchronousdynamic RAM (SDRAM), nonvolatile/Flash-type memory, or any other type ofmemory. In the illustrated embodiment, program instructions 4022 may beconfigured to implement various interfaces, methods and/or data forcontrolling operations of camera 4090 and for capturing and processingimages with integrated camera 4090 or other methods or data, for exampleinterfaces and methods for capturing, displaying, processing, andstoring images captured with camera 4090. In some embodiments, programinstructions and/or data may be received, sent or stored upon differenttypes of computer-accessible media or on similar media separate fromsystem memory 4020 or computer system 4000.

In one embodiment, I/O interface 4030 may be configured to coordinateI/O traffic between processor 4010, system memory 4020, and anyperipheral devices in the device, including network interface 4040 orother peripheral interfaces, such as input/output devices 4050. In someembodiments, I/O interface 4030 may perform any necessary protocol,timing or other data transformations to convert data signals from onecomponent (e.g., system memory 4020) into a format suitable for use byanother component (e.g., processor 4010). In some embodiments, I/Ointerface 4030 may include support for devices attached through varioustypes of peripheral buses, such as a variant of the Peripheral ComponentInterconnect (PCI) bus standard or the Universal Serial Bus (USB)standard, for example. In some embodiments, the function of I/Ointerface 4030 may be split into two or more separate components, suchas a north bridge and a south bridge, for example. Also, in someembodiments some or all of the functionality of I/O interface 4030, suchas an interface to system memory 4020, may be incorporated directly intoprocessor 4010.

Network interface 4040 may be configured to allow data to be exchangedbetween computer system 4000 and other devices attached to a network4085 (e.g., carrier or agent devices) or between nodes of computersystem 4000. Network 4085 may in various embodiments include one or morenetworks including but not limited to Local Area Networks (LANs) (e.g.,an Ethernet or corporate network), Wide Area Networks (WANs) (e.g., theInternet), wireless data networks, some other electronic data network,or some combination thereof. In various embodiments, network interface4040 may support communication via wired or wireless general datanetworks, such as any suitable type of Ethernet network, for example;via telecommunications/telephony networks such as analog voice networksor digital fiber communications networks; via storage area networks suchas Fibre Channel SANs, or via any other suitable type of network and/orprotocol.

Input/output devices 4050 may, in some embodiments, include one or moredisplay terminals, keyboards, keypads, touchpads, scanning devices,voice or optical recognition devices, or any other devices suitable forentering or accessing data by computer system 4000. Multipleinput/output devices 4050 may be present in computer system 4000 or maybe distributed on various nodes of computer system 4000. In someembodiments, similar input/output devices may be separate from computersystem 4000 and may interact with one or more nodes of computer system4000 through a wired or wireless connection, such as over networkinterface 4040.

As shown in FIG. 10, memory 4020 may include program instructions 4022,which may be processor-executable to implement any element or action tosupport integrated camera 4090, including but not limited to imageprocessing software and interface software for controlling camera 4090.In some embodiments, images captured by camera 4090 may be stored tomemory 4020. In addition, metadata for images captured by camera 4090may be stored to memory 4020.

Those skilled in the art will appreciate that computer system 4000 ismerely illustrative and is not intended to limit the scope ofembodiments. In particular, the computer system and devices may includeany combination of hardware or software that can perform the indicatedfunctions, including computers, network devices, Internet appliances,PDAs, wireless phones, pagers, video or still cameras, etc. Computersystem 4000 may also be connected to other devices that are notillustrated, or instead may operate as a stand-alone system. Inaddition, the functionality provided by the illustrated components mayin some embodiments be combined in fewer components or distributed inadditional components. Similarly, in some embodiments, the functionalityof some of the illustrated components may not be provided and/or otheradditional functionality may be available.

Those skilled in the art will also appreciate that, while various itemsare illustrated as being stored in memory or on storage while beingused, these items or portions of them may be transferred between memoryand other storage devices for purposes of memory management and dataintegrity. Alternatively, in other embodiments some or all of thesoftware components may execute in memory on another device andcommunicate with the illustrated computer system 4000 via inter-computercommunication. Some or all of the system components or data structuresmay also be stored (e.g., as instructions or structured data) on acomputer-accessible medium or a portable article to be read by anappropriate drive, various examples of which are described above. Insome embodiments, instructions stored on a computer-accessible mediumseparate from computer system 4000 may be transmitted to computer system4000 via transmission media or signals such as electrical,electromagnetic, or digital signals, conveyed via a communication mediumsuch as a network and/or a wireless link. Various embodiments mayfurther include receiving, sending or storing instructions and/or dataimplemented in accordance with the foregoing description upon acomputer-accessible medium. Generally speaking, a computer-accessiblemedium may include a non-transitory, computer-readable storage medium ormemory medium such as magnetic or optical media, e.g., disk orDVD/CD-ROM, volatile or non-volatile media such as RAM (e.g. SDRAM, DDR,RDRAM, SRAM, etc.), ROM, etc. In some embodiments, a computer-accessiblemedium may include transmission media or signals such as electrical,electromagnetic, or digital signals, conveyed via a communication mediumsuch as network and/or a wireless link.

The methods described herein may be implemented in software, hardware,or a combination thereof, in different embodiments. In addition, theorder of the blocks of the methods may be changed, and various elementsmay be added, reordered, combined, omitted, modified, etc. Variousmodifications and changes may be made as would be obvious to a personskilled in the art having the benefit of this disclosure. The variousembodiments described herein are meant to be illustrative and notlimiting. Many variations, modifications, additions, and improvementsare possible. Accordingly, plural instances may be provided forcomponents described herein as a single instance. Boundaries betweenvarious components, operations and data stores are somewhat arbitrary,and particular operations are illustrated in the context of specificillustrative configurations. Other allocations of functionality areenvisioned and may fall within the scope of claims that follow. Finally,structures and functionality presented as discrete components in theexample configurations may be implemented as a combined structure orcomponent. These and other variations, modifications, additions, andimprovements may fall within the scope of embodiments as defined in theclaims that follow.

What is claimed is:
 1. A lens system, comprising: a plurality ofelements arranged along a folded optical axis of the lens system,wherein the plurality of elements includes, in order along the foldedoptical axis from an object side to an image side: a first lens elementon a first portion of the folded optical axis having a convexobject-side surface in the paraxial region; a light folding elementconfigured to redirect light from the first lens element to a secondportion of the folded optical axis; a second lens element on the secondportion of the folded optical axis; a third lens element on the secondportion of the folded optical axis having a concave image-side surfacein the paraxial region; and a fourth lens element on the second portionof the folded optical axis.
 2. The lens system as recited in claim 1,wherein the first lens element has positive refractive power, and thesecond lens element has negative refractive power.
 3. The lens system asrecited in claim 1, wherein the lens system further comprises anaperture stop located between the object side of the lens system and thelight folding element.
 4. The lens system as recited in claim 1, whereinthe lens system provides a 35 mm equivalent focal length in the range of75-120 mm and less than 6 mm of Z-height measured from a front vertex ofthe lens system to a rear vertex of the folding element.
 5. The lenssystem as recited in claim 1, wherein the lens system provides a 35 mmequivalent focal length in the range of 55-140 mm and less than 6.5 mmof Z-height measured from a front vertex of the lens system to a rearvertex of the folding element.
 6. The lens system as recited in claim 1,wherein the first and fourth lens elements are formed of opticalmaterials with Abbe number Vd>40, and the second lens element is formedof an optical material with Abbe number Vd<30.
 7. The lens system asrecited in claim 1, wherein the first lens element is formed of anoptical material with Abbe number Vd>40, and the second lens element isformed of an optical material with Abbe number Vd<30.
 8. The lens systemas recited in claim 1, wherein the lens system satisfies one or more ofthe relationships:0.4<|f/f1|<10.8<|f/f2|<1.60.05<|R4f−R4r|/|R4f+R4r|<0.8 where f is effective focal length of thelens system, f1 is focal length of the first lens element, f2 is focallength of the second lens element, R4 f is radius of curvature of theobject-side surface of the fourth lens element, and R4 r is radius ofcurvature of the image side surface of the fourth lens element.
 9. Thelens system as recited in claim 1, wherein at least one surface of atleast one of the plurality of lens elements is aspheric.
 10. The lenssystem as recited in claim 1, wherein at least one of the lens elementsis formed of lightweight polymer or plastic material.
 11. The lenssystem as recited in claim 1, wherein the light folding element is aprism.
 12. The lens system as recited in claim 11, wherein an image sidesurface of the first lens element is flat/plano, and wherein the imageside surface of the first lens element is in contact with the objectside surface of the prism.
 13. The lens system as recited in claim 1,wherein effective focal length of the lens system is within a range of6.5 millimeters to 14 millimeters.
 14. The lens system as recited inclaim 1, wherein focal ratio (F/#) of the lens system is within a rangeof 2.2 to
 3. 15. The lens system as recited in claim 1, wherein fullfield of view (FOV) of the lens system is within a range of 20.4° to42.2°.
 16. A camera, comprising: a photosensor configured to capturelight projected onto a surface of the photosensor; and a folded lenssystem configured to refract light from an object field located in frontof the camera to form an image of a scene at an image plane at or nearthe surface of the photosensor, wherein the lens system comprises fourrefractive lens elements arranged along a folded optical axis of thecamera from an object side to an image side and a light folding elementlocated between a first and second lens element from the object side andconfigured to redirect light from a first axis onto a second axis;wherein the folded lens system provides a 35 mm equivalent focal lengthin the range of 55-140 mm and less than 6.5 mm of Z-height measured froma front vertex of the lens system to a rear vertex of the foldingelement.
 17. The camera as recited in claim 16, wherein effective focallength of the lens system is within a range of 6.5 millimeters to 14millimeters, and wherein the photosensor is between 4 millimeters and 8millimeters in a diagonal dimension.
 18. The camera as recited in claim16, wherein the photosensor is configured to move on one or more axesrelative to the lens system to adjust focus of the camera.
 19. A device,comprising: one or more processors; one or more cameras; and a memorycomprising program instructions executable by at least one of the one ormore processors to control operations of the one or more cameras;wherein at least one of the one or more cameras is a camera comprising:a photosensor configured to capture light projected onto a surface ofthe photosensor; and a folded lens system configured to refract lightfrom an object field located in front of the camera to form an image ofa scene at an image plane proximate to the surface of the photosensor,wherein the lens system comprises four refractive lens elements arrangedalong a folded optical axis of the lens system from an object side to animage side and a light folding element configured to redirect light fromthe first lens element on the object side to a second portion of thefolded optical axis; wherein the lens system lens system provides a 35mm equivalent focal length in the range of 55-140 mm and less than 6.5mm of Z-height measured from a front vertex of the lens system to a rearvertex of the folding element.
 20. The device as recited in claim 19,wherein the lens system further comprises at least one aperture stoplocated between a front vertex of the lens system and the light foldingelement.